Surface fixation of poly(ethylene glycol)via photodimerization of cinnamate group

This article reports a new fixation method for hydrophilic layers on substrates. The method is based on the photochemistry of the cinnamate group, which is capable of intermolecular dimerization upon ultraviolet (UV) light irradiation. The method used was as follows. First, two photoreactive polymers were sequentially coated on a polymeric surface: a polycinnamate as an adhesive layer and a cinnamated poly(ethylene glycol) (PEG) as a hydrophilic layer. Subsequently the surface was exposed to UV light. No delamination occurred upon washing with water and methanol; the photoreactive PEG was chemically bonded onto the surface via the polycinnamate. The higher the molecular weight of PEG, the higher the wettability of the surface was formed. Minimal cell adhesion was observed on such a surface. The biomedical applications of the method are discussed. © 1993 John Wiley & Sons, Inc.     

Micellization and Thermogelation of Poly(ether urethane)s Comprising Poly(ethylene glycol) and Poly(propylene glycol)

A series of multiblock poly(ether urethane)s comprising poly(ethylene glycol) (PEG), and poly(propylene glycol) (PPG) segments were synthesized. Their aqueous solutions exhibited thermogelling behavior at critical gelation concentrations (CGC) ranging from 8 to 12 wt%. The composition and structural information of the copolymers were studied by GPC and ¹H NMR. The critical micellization concentration (CMC) and thermodynamic parameters for micelle formation were determined at different temperatures. The temperature response of the copolymer solutions were studied and found to be associated with the composition of the copolymers.     

Photocrosslinked hydrogels based on copolymers of poly(ethylene glycol) and lysine

A group of new, water-soluble poly(ether-urethane)s, derived from poly(ethylene glycol) and the amino acid L -lysine, provide pendent carboxylic acid groups along the polymer backbone at regular intervals. The carboxylic acid groups were utilized for the attachment of acrylate and methacrylate pendent chains (hydroxyethyl acrylate, hydroxyethyl methacrylate, aminoethyl methacrylate, and aminoethyl methacrylamide), leading to functionalized polymers. The pendent chains were attached via ester and/or amide bonds having different degrees of hydrolytic stability. The attachment reactions proceeded with high yields (up to 95%). The functionalized polymers were subsequently photopolymerized (UV irradiation) to obtain crosslinked hydrogels. Crosslinked membranes with the highest degree of mechanical strength were obtained when the crosslinking reaction was performed in dioxane with benzoin methyl ether (0.1 wt %) as the initiator. the crystallinity, thermomechanical properties, and hydrolytic stability of the crosslinked membranes were studied. All membranes were transparent and highly swellable (equilibrium water content: 64–88%). The tensile strength in the swollen state ranged from 0.15 to 1.09 MPa. Under physiological conditions (phosphate buffered water, 0.1M, pH 7.4, 37°C) the hydrolytic stability of the hydrogels varied depending on the bonds used in the attachment of the acrylate pendent chains: Hydrogels with hydroxyethyl acrylate pendent chains dissolved within 30 days, while hydrogels containing aminoethyl methacrylamide pendent chains remained unchanged throughout a 30 day period. Using high molecular weight FITC-dextrans as model compounds, complete release from the swollen hydrogels required between 60 and 150 h. Overall, the evaluation of poly(ethylene glycol)-lysine derived, photocrosslinked hydrogels indicated that these materials provide a range of potentially useful properties. © 1994 John Wiley & Sons, Inc.     

Thermal,morphological, mechanical and aging properties of polylactide blends with poly(ether urethane) based on chain-extension reaction of poly(ethylene glycol) using diisocyanate

Poly(ether urethane)s(PEU), including PEUI15 and PEUH15, were prepared through chain-extension reaction of poly(ethylene glycol)(PEG-1500) using diisocyanate as a chain extender, including isophorone diisocyanate(IPDI) and hexamethylene diisocyanate(HDI). These PEUs were used to toughen polylactide(PLA) by physical and reactive blending.Thermal, morphological, mechanical and aging properties of the blends were investigated in detail. These PEUs were partially compatible with PLA. The elongation at break of the reactive blends in the presence of triphenyl phosphate(TPP)for PLA with PEUH15 or PEUI15 was much higher than that of the physical blends. The aging test was carried out at-20 °C for 50 h in order to accelerate the crystallization of PEUs. The PEUs in the PLA/PEU blends produced crystallization and formed new phase separation with PLA, resulting in the declined toughness of blends. Fortunately, under the aging condition,although PEUH15 in blends could also form crystallization, the reactive blend of PLA/PEUH15/TPP(80/20/2) had higher toughness than the other blends. The elongation at break of PLA/PEUH15/TPP(80/20/2) dropped to 287% for the aging blend from 350% for the original blend. The tensile strength and modulus of PLA/PEUH15/TPP blend did not change obviously because of the crystallization of PEUH15.     

Regioselective grafting of poly(ethylene glycol) onto chitosan and the properties of the resulting copolymers

PEG was grafted onto chitosan regioselectively at the hydroxyl groups with phthaloylchitosan as an intermediate. After the graft reaction, the phthaloyl groups were deprotected to give chitosan-g-PEG copolymers with free amino groups. The chemical structure of the graft copolymers was confirmed by FT-IR, (1)H and (13)C NMR spectroscopy. The resulting graft copolymers showed improved thermal stability compared to the original chitosan, and showed a lower thermal transition temperature at around 185 degrees C. Chitosan-g-PEG exhibited a high affinity not only for aqueous acid but also for some organic solvents because of the presence of abundant free amino groups and PEG branches, and it exhibited higher hygroscopicity and moisture retention ability than chitosan. [structure: see text]     

Corrosion inhibition of zinc-plated steel in 0.5, 1 and 1.5 M sulphuric acid by poly(ethylene glycol)

The effect of poly(ethylene glycol) (PEG) 4000 on the corrosion of zinc-plated steel in H₂SO₄ has been investigated over a wide range of conditions. It was found that the corrosion rate depends upon exposure time. The rate of corrosion goes down rapidly to reach a low value, which is an almost constant value within 5 hr under most conditions. This trend was also found by Growock and Lopp for the inhibition of steel corrosion in HCl with 3-phenyl-2-propyl-1-ol. Other workers have linked this slow fall-off in the corrosion rate to film formation. The corrosion rate was found to decrease slowly with increasing PEG concentration, and to increase slowly with acid concentration for all conditions. The effect of temperature on corrosion rate was found to be similar to that of acid concentration. The corrosion rate decreased exponentially with poly(ethylene glycol) concentration. The percentage inhibition reached a value of 48.93 for a PEG concentration of 4 ppm: to double this, the concentration had to be increased to 40,000 ppm. Sulphuric acid titration against sodium hydroxide showed no change in acid concentration during the corrosion protection process, thus supporting the film protection theory     

Surface modification of hydroxyapatite to avoid bacterial adhesion

Hydroxyapatite was surface-modified by adsorption of nonionic polymers carrying phosphate groups as anchoring groups. A combination of alcohol ethoxylate and alkyl phosphate was also used. The possibility of interfering with early microbial colonization on apatite, mimicking the tooth surface, was investigated using radiolabelledStreptococcus mutans as model bacteria. The polymers, a nonionic cellulose ether and an EO/PO block copolymer based on polyglycerol as starting alcohol, were effective in buffer but gave only limited reduction of bacterial adhesion when the apatite had been pretreated with saliva. A 11 molar mixture of alcohol ethoxylate and alkyl phosphate was effective both with and without saliva, however. Studies with¹⁴C-labeled compounds, as well as microelectrophoresis experiments, indicate that an unsymmetrical double layer is formed on the apatite surface with predominantly alkyl phosphate in the inner layer and with alcohol ethoxylate pointing towards the water phase.     

New Poly(propylene glycol)‐ and Poly(ethylene glycol)‐Based Polymer Gelators with L‐Lysine

Summary: New polymer gelators consisting of poly(propylene glycol) or poly(ethylene glycol) and L ‐lysine‐based low‐molecular‐weight gelators have been developed. These polymer gelators were synthesized according to a simple procedure with high reaction yield, and formed organogels in many organic solvents. The organogelation mechanism was proposed from the transmission electron microscopy and FTIR spectroscopy studies.

Structures of the polymer gelators synthesized here.     

Poly（L—lactide）—Poly（ethylene glycol） Multiblock Copolymers：Synthesis and Properties

Poly (L-lactide)-poly (ethylene glycol) multiblock copolymers with predetermined block lengths were synthesized by polycondensation of PLA diols and PEG diacids. These copolymers presented special properties, such as better miscibility between the two components, low crystallinity and better hydrophilicity, which can be modulated by adjusting the block lengths of the two components.     

Surface modification of SPEU films by ozone induced graft copolymerization to improve hemocompatibility

Surface modification of segmented poly(ether urethane) (SPEU) by graft copolymerization with N,N′-dimethyl-N-methacryloyloxyethyl-N-(3-sulfopropyl) ammonium (DMMSA), a zwitterionic sulfobetaine structure, was conducted. A simple two-step procedure for grafting of DMMSA onto the surface of SPEU film was used. The surface was first treated with ozone to introduce active hydroperoxide groups. The active surface was then exposed to the DMMSA solution in the sealed tube. Grafted SPEU film was characterized by ATR–FTIR, XPS and contact angle measurement. ATR–FTIR and XPS investigations confirmed the graft copolymerization. The monomer concentration, copolymerization temperature and time were varied to maximize the efficiency of DMMSA grafting. The equilibrium water content (EWC) and contact angle measurements showed that the hydrophilicity of the film had been greatly improved. The blood compatibility of the grafted films was evaluated by platelet adhesion in platelet rich plasma (PRP), deposits in blood control and protein adsorption in bovine fibrinogen using SPEU film as the control. No platelet adhesion and no thrombus were observed for the grafted films incubated in PRP for 300 min and in blood for 120 min, respectively. The protein adsorption was reduced on the grafted films after incubation in bovine fibrinogen for 120 min. These results proved that improved blood compatibility was obtained by grafting this new zwitterionic sulfobetaine structure monomer onto SPEU film.     

Surface Modification of Carbon Nanotube by Poly(ethylene glycol) for the Preparation of Poly(vinyl alcohol) Nanocomposite

Herein, PEGylated multi-walled carbon nanotube (MWNT) was prepared for the successive fabrication of poly(vinyl alcohol) PVA/MWNT nanocomposite film by solution casting. The surface modified MWNT showed a good colloidal stability in a polar solvent, i.e., water. Also, the PEGylated MWNT had an improved dispersion stability in aqueous PVA solution. The mixture of PEGylated MWNT and PVA dissolved in water was film casted and the dispersion uniformity and corresponding improvement of electrical conductivity were investigated. The electrical conductivity of PVA/modified MWNT composite film was three-fold higher than that of PVA/pristine MWNT composite film due to the much improved distribution uniformity of modified MWNT in PVA matrix.     

Surface modification of polydimethylsiloxane with photo-grafted poly(ethylene glycol) for micropatterned protein adsorption and cell adhesion

In this study, we applied photo-induced graft polymerization to micropatterned surface modification of polydimethylsiloxane (PDMS) with poly(ethylene glycol). Two types of monomers, polyethylene glycol monoacrylate (PEGMA) and polyethylene glycol diacrylate (PEGDA), were tested for surface modification of PDMS. Changes in the surface hydrophilicity and surface element composition were characterized by contact angle measurement and electron spectroscopy for chemical analysis. The PEGMA-grafted PDMS surfaces gradually lost their hydrophilicity within two weeks. In contrast, the PEGDA-grafted PDMS surface maintained stable hydrophilic characteristics for more than two months. Micropatterned protein adsorption and micropatterned cell adhesion were successfully demonstrated using PEGDA-micropatterned PDMS surfaces, which were prepared by photo-induced graft polymerization using photomasks. The PEGDA-grafted PDMS exhibited useful characteristics for microfluidic devices (e.g. hydrophilicity, low protein adsorption, and low cell attachment). The technique presented in this study will be useful for surface modification of various research tools and devices.     

Water-soluble dendrimer–poly(ethylene glycol) starlike conjugates as potential drug carriers

The design and synthesis of a new dendrimer–poly(ethylene glycol) (PEG) conjugate that may be used as a model drug carrier are described. The starting material is a polyether dendrimer with two different types of chain end functionalities. The dendritic assembly is made water soluble through attachment of short PEG chains to the dendrimer via one type of functionality. The remaining chain end functionalities then were used to incorporate model drug molecules of varying polarity into the modified dendrimer. Cholesterol and two amino acid derivatives were selected as model drugs for attachment through their respective hydroxyl, carboxylic acid, and amino functional groups to the dendrimer via carbonate, ester, and carbamate linkages. The resulting water-soluble dendrimer-model drug conjugates were characterized by matrix-assisted laser desorption ionization time of flight (MALDI-TOF) mass spectrometry. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3492–3503, 1999     

Surface covalent encapsulation of multiwalled carbon nanotubes with poly(acryloyl chloride) grafted poly(ethylene glycol)

Multiwall carbon nanotube (MWNT) was grafted with polyacrylate‐g‐poly (ethylene glycol) via the following two steps. First, hydroxyl groups on the surface of acid‐treated MWNT reacted with linear poly(acryloyl chloride) to generate graft on MWNT; secondly, the remaining acryloyl chloride groups were subjected to esterification with poly(ethylene glycol) leading the grafted chains on the surface of MWNTs. Thus obtained grafted MWNT was characterized using Fourier transform infrared spectrometer, transmission electron microscopy, and X‐ray photoelectron spectroscopy. Thermogravimetric analysis showed that the weight fraction of grafted polymers amounted to 80% of the modified MWNT. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6880–6887, 2006     

Parameters affecting transition temperatures of poly(lactic acid‐co‐polydiols) copolymer‐based polyester urethanes and their shape memory behavior

A series of polyester urethanes (PEUs) comprising poly(lactic acid‐co‐polydiol) copolymers as a soft segment, 4,4′‐diphenylmethane diisocyanate (MDI) and 1,4‐butanediol (BDO) as a hard segment were systematically synthesized. Soft segments, which were block copolymers of L ‐lactide (LA) and polydiols such as poly(ethylene glycol) and poly(trimethylene ether glycol), were prepared via ring opening polymerization. Glass transition temperatures (T_g) of the obtained PEUs were found strongly dependent on properties of copolymer soft segments. By simply changing composition ratio, type and molecular weight of polydiols in the soft segment preparation step, T_g of PEU can be varied in the broad range of 0–57°C. The synthesized PEUs exhibited shape memory behavior at their transition temperatures. PEUs with hard segment ratio higher than 65 mole percent showed good shape recovery. These findings suggested that it is important to manipulate molecular structure of the copolymer soft segment for a desirable transition temperature and design optimal soft to hard segment ratio in PEU for good shape recovery. Copyright © 2011 John Wiley & Sons, Ltd.     

Brush‐like poly(ethylene glycol) grafting on SiO2 nanoparticles with in‐situ polymerization

This work presents the grafting of poly(ethylene glycol) (PEG) on the SiO₂ nanoparticles by the use of the azo‐groups bonded SiO₂ as a radical initiator and poly(ethylene glycol) methyl ether methacrylate (PEGMA) as a macromonomer, respectively. Then a kind of organic–inorganic composite particles with brush‐like PEG fixed covalently on the SiO₂ nanoparticles, SiO₂–PEG, is synthesized. The successful synthesis of SiO₂–PEG is confirmed by FT‐IR, XPS, and TEM techniques. Results show that the conversion degree of PEGMA can reach nearly 30% while the PEG graft amount accounts for ca. 43% of the total weight of the composite particles. After the PEG is grafted on the SiO₂ nanoparticles, the mobility of PEG chains is hindered by the proximity of oxide phase of SiO₂. As a result, PEG phase is strongly disturbed. Consequently, the grafted PEG melts at a low temperature with small quantity of heat enthalpy. Copyright © 2014 John Wiley & Sons, Ltd.     

Enhanced separation of albumin-poly(ethylene glycol) by combination of ultrafiltration and electrophoresis

Separation of bovine serum albumin (BSA) from poly(ethylene glycol) (PEG) through ultrafiltration membranes has been investigated. Concentration polarization by BSA represents a strong limitation to the transmission of PEG through a porous membrane. The application of an electric field normal to the membrane can help to reduce BSA concentration polarization and to enhance PEG transmission, both in ultrafiltration and in diafiltration mode. A range of solution compositions of BSA and PEG has been investigated. The contribution of electrokinetic phenomena is measured by specific experiments.     

Kinetics and Modeling of Vinyl Acetate Graft Polymerization from Poly(ethylene glycol)

A kinetic model for the graft polymerization of VAc from PEG was developed using the method of moments. Experiments were carried out to verify the model. The effect of various parameters, such as initiator concentration, temperature, and PEG molecular weight on the polymerization kinetics was examined. Polymerization rate, grafting efficiency, graft copolymer molecular weight, and PEG grafted ratio were measured. The model was in good agreement with the experimental data. No gel effect was observed at the studied PEG/VAc weight ratio of 1:1. The chain transfer constant to PEG was correlated to be . The model was also applied in a semi‐batch reaction and compared with the experimental results.

     

Synthesis of degradable functional poly(ethylene glycol) analogs as versatile drug delivery carriers

Poly(ethylene glycol) (PEG) is widely used as a water soluble carrier for polymer-drug conjugates. Herein, we report degradable linear PEG analogs (DPEGs) carrying multifunctional groups. The DPEGs were synthesized by a Michael addition based condensation polymerization of dithiols and PEG diacrylates (PEGDA) or dimethacrylates (PEGDMA). They were stable at pH 7.4 but quickly degraded at pH 6.0 and 5.0. Thus, DPEGs could be used as drug carriers without concern for their retention in the body. DPEGs could be made to carry such functional groups as terminal thiol or (meth)acrylate and pendant hydroxyl groups. The functional groups were used for conjugation of drugs and targeting groups. This new type of PEG analog will be useful for drug delivery and the PEGylation of biomolecules and colloidal particles.     

Segmented block copolymers of poly(ethylene glycol) and poly(ethylene terephthalate)

A new series of segmented copolymers were synthesized from poly(ethylene terephthalate) (PET) oligomers and poly(ethylene glycol) (PEG) by a two‐step solution polymerization reaction. PET oligomers were obtained by glycolysis depolymerization. Structural features were defined by infrared and nuclear magnetic resonance (NMR) spectroscopy. The copolymer composition was calculated via ¹H NMR spectroscopy. The content of soft PEG segments was higher than that of hard PET segments. A single glass‐transition temperature was detected for all the synthesized segmented copolymers. This observation was found to be independent of the initial PET‐to‐PEG molar ratio. The molar masses of the copolymers were determined by gel permeation chromatography (GPC). © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4448–4457, 2004